Does the Macbook Pro you have still have a removable HDD or SSD? I would try disconnecting it and try to boot off Internet Recovery. Just to see if it works. Same goes with unplugging any other attached drive.
Sometimes a dead drive can lock up OS X from booting. Even if it isn't the boot drive.
Have you tried with an external keyboard? If the onboard one is damaged you may not be actually hitting the keys.
Also, when you start it up do you hear the chime?
Please also explain exactly what you mean by "stuck in startup". Do you see anything on the screen when you start it?